In recent years, a so-called electric compressor has been developed using an electric motor as a drive source of a compressor for compressing a refrigerant in an automotive air conditioner.
Such an electric compressor is still under development, and there are various problems to be solved. Particularly, there are many problems at the start, and various proposals have been made for quick and reliable start (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent Laid-Open No. 2007-151318
One of the problems at the start of the electric compressor is that the electric compressor cannot be smoothly started at high temperature due to a temperature characteristic of a power transistor provided on a drive control board of the electric compressor.
The power transistor has a temperature characteristic that a current that can be carried becomes lower at higher temperatures, and includes a protection circuit that stops an operation of the electric compressor at high temperature. Thus, when the electric compressor is to be started when in a high temperature state, the protection circuit of the power transistor is operated to stop the operation of the electric compressor and prevent the start.
Thus, as shown in FIG. 7, when the protection circuit of the power transistor is operated, it is necessary that the electric compressor is rotated at a low speed for a certain time and a rotational speed of the electric compressor is manually increased after the certain time passes and the power transistor is sufficiently cooled, which takes time to start the electric compressor.
The present invention is achieved on the basis of such technical problems, and has an object to provide a control device for an electric compressor and a start control method of an electric compressor that can smoothly and reliably start the electric compressor even at high temperature.